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Kettlebells, with their unique shape, are designed for ballistic movements, which take the body through a more natural range of motion (and also torch calories), says Rodocoy. Generally, the kettlebells' instability provides a greater total-body workout because the stabilizer muscles, especially in the core, have to work harder to maintain control of the weight during the exercise. Barbells, thanks to their relative stability, have the awesome benefit of allowing you to load up a lot heavier on exercises such as squats, deadlifts, and bench presses, for greater lean-muscle building, strength gains, and calorie burning. Dumbbells, on the other hand, let you split the load, so each side does the same work (and you can't "cheat" by letting the stronger arm take over).
How to Progress from One Weight Type to Another
So how do you decide which to use in your workout? Typically, the aim of resistance training is to progress in the amount of weight you can move (an indication of strength) and the control with which you do it (an indication of stability). For example, after you've mastered bodyweight squats, you can increase your strength by trying squats while holding a single dumbbell or kettlebell in both hands in front of your chest, suggests Rodocoy. Next, go for two dumbbells or kettlebells held down by your sides for double the weight and more external pull, which creates a greater core challenge. Then you might try a back-loaded barbell squat, which allows you to increase the resistance up to as many plates as you can handle. (Don’t worry: Your core muscles will still be recruited to balance the weight through the exercise.) You can follow a similar progression for deadlifts, too.
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For upper-body moves such as bent-over rows or chest presses, Rodocoy recommends emphasizing stabilization. He suggests going from the relative steadiness of a barbell to less-stable dumbbells and then to kettlebells, which require even more control.
Advanced power-training ballistic moves, such as kettlebell swings, are best done with kettlebells (or medicine balls). (Rodocoy cringes whenever he sees someone do kettlebell swings with a dumbbell.)
The other important element is making sure you’re using an appropriate amount of weight. “If you can do 10 reps but could do 25, take it up,” says Rodocoy. “But leave a couple reps in the tank; if you can do three or four more, but not at the sacrifice of your form, then you’re good.” Rodocoy doesn’t just see this as a ladder you keep climbing up, however. He emphasizes mixing it up, both in terms of type of weight and amount of weight, as well as types of exercises you’re doing. “The greatest changes happen when you constantly challenge your body,” he says.
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Amy Roberts is a certified personal trainer.